1. Field of the Invention
The present invention relates to a vehicle power supply control apparatus for controlling power supplied to various devices powered by a vehicle battery, and particularly, electric devices of an air conditioning system.
2. Description of the Related Art
An air conditioning system of an electric vehicle driven by a battery-powered vehicle-driving motor includes electric devices such as an electric heater and a motor-driven compressor. Usually, electric power is supplied to the vehicle-driving motor prior to such battery-powered devices used in the air conditioning system.
For example, electric power to be supplied to an electric heater is controlled according to a calculated total demand for electric power to be used by a vehicle. The target amount of the electric power (hereinafter referred to as current target power) to be supplied to the electric heater is calculated based on a previously calculated amount of electric power (hereinafter referred to precedent target power). That is, the current target power is obtained from the precedent target power by adding or subtracting an amount of power to be changed to or from the precedent target power.
If the current target power to be supplied to the electric heater is smaller than an allowed amount (hereinafter referred to as allowed power) determined according to the calculated total demand for electric power to be used by the vehicle, the electric heater is fully supplied with sufficient power. On the other hand, the electric heater is supplied with a less amount of the electric power than the target power if the target power is larger than the allowed power. In this case, it is difficult for the electric heater to provide a suitable heating performance.